2012 Annual Report
1a.Objectives (from AD-416):
Conserve and distribute a wide range of small grains genetic diversity and associated information to researchers and breeders worldwide. Strategically evaluate (phenotype) small grains genetic resources for priority biotic and abiotic stress resistance, quality factors, and other priority agronomic traits, and incorporate phenotypic data into the Germplasm Resources Information Network (GRIN) and/or other databases. Make newly-found major genes and adult-plant genes for Ug99 stem rust resistance available to breeders for incorporation into adapted germplasm for the United States. Characterize the genetic variability in small grain genebank collections via genotyping with leading edge genetic marker technology and geographic information systems.
1b.Approach (from AD-416):
Acquisition priorities include the wild relatives of Triticum, Hordeum, Avena, and Oryza to fill species and ecogeographic gaps in the crop collections. Geographic regions of special interest are the Caucasus and Central Asia. These gaps will be primarily addressed by collection expeditions and exchanges with other genebanks. All acquisitions will follow USDA-APHIS protocols to avoid the introduction of harmful diseases and insects. Mapping populations and other genetic resources developed in the Barley and Wheat Coordinated Agricultural Projects (CAP) will be stored and distributed as part of National Small Grains Collection (NSGC) genetic stock collections. Established procedures will be used to maintain and regenerate all NSGC germplasm accessions, with special attention to seed preparation and planting, plant pathogen monitoring, harvest, and laboratory processing. Seed will be provided to the National Center for Genetic Resources Preservation for safety back up. New information technology will be identified to increase the quality, accessibility, and value of the data collected. The project will either conduct or coordinate systematic evaluations of important traits. The small grains Crop Germplasm Committees (CGC) have previously developed lists of descriptors for evaluation and are consulted regularly for evaluation priorities. Several evaluations, ongoing for a number of years and considered high priority by the CGC, will be continued. Ug99 stem rust resistance research will focus on identifying new major and adult-plant genes in wheat landraces and making the new sources of resistance available to breeders for transfer to adapted germplasm for all regions of the U.S. Evaluation of rice germplasm will be coordinated at the USDA-ARS Dale Bumpers National Rice Research Center, Stuttgart, Arkansas and data will be returned to Aberdeen for inclusion in GRIN. SSR markers will be employed to genotype the NSGC core subsets of wheat and barley, totaling 5,500 and 2,577 accessions, respectively. To eliminate variation due to heterogeneity within accessions, single-plant-selections for each core accession will be generated for genotyping. Resulting data will be analyzed to better understand genetic variation within the collection, including the relationship between variation and geographic origin of accessions. Country, state/province, locality, and latitude/longitude data for NSGC accessions are maintained in GRIN. Traits of interest will be mapped and analyzed using GIS software and appropriate statistical techniques. Because stem and stripe rust of wheat and barley are of current concern worldwide, priority will be given to mapping the geographic origin of resistance. Accession genetic diversity in the core collections, based on molecular marker data will be mapped to better understand its relationship to accession geographic origin, to elucidate relations between geographic patterns of molecular diversity and trait diversity, and to do gap analysis to identify priority areas for future collection.
The National Small Grains Collection (NSGC) presently holds 140,277 accessions of the small grains (wheat, barley, oat, rye, triticale, rice, and related wild species). Viability testing of more than 17,000 accessions was completed to assure that high-quality seed is distributed to scientists. More than 6,300 accessions were regenerated in the past year. This resulted in the harvest of fresh seed to be placed in the NSGC storages, replacing older seed. More than 100,000 accession seed samples were distributed to scientists in the past year. Ploidy levels (chromosome numbers) were determined for more than 1,000 landrace wheat accessions.
NSGC germplasm distributed to scientists. More than 100,000 NSGC seed samples were distributed from the USDA-ARS National Small Grains Germplasm Research Facility, Aberdeen, Idaho, to scientists in more than 860 separate requests. This represents the largest one-year total for distributions. Thirty percent of the requests were from scientists outside the U.S. Germplasm is the basis of small grains improvement. Seed was distributed for research purposes and for germplasm enhancement, including the development of new, improved cultivars for release to farmers.
Field resistance to Ug99 stem rust in wheat landraces. New and virulent races of the stem rust pathogen have arisen in East Africa. These new races, called Ug99, threaten US wheat production. Over the past several years, ARS researchers from Aberdeen, Idaho screened more than 2500 landrace spring wheats from the National Small Grains Collection at a testing site in Njoro, Kenya, and found 278 Ug99-resistant accessions. Some of these accessions may represent novel resistance sources useful for protecting the US wheat crop against the new stem rust races. Researchers will next study the genetic basis of the resistance to determine which sources will have the greatest value for plant breeding.
Adhikari, T.B., Gurung, S., Hansen, J., Jackson, E.W., Bonman, J.M. 2012. Association mapping of quantitative trait loci responsible for resistance to Bacterial Leaf Streak and Spot Blotch in spring wheat landraces. The Plant Genome. 5:1-16. doi:10.3835/plantgenome2011.12.0032.
Gurung, S., Mamid, S., Bonman, J.M., Jackson, E.W., Del Rio, L.E., Acevedo, M., Adhikari, T.B. 2011. Identification of novel genomic regions associated with resistance to Pyrenophora tritici-repentis races 1 and 5 in spring wheat landraces using association analysis. Theoretical and Applied Genetics. 123:1029-1041.
Goates, B. 2011. Identification of new pathogenic races of common bunt and dwarf bunt fungi, and evaluation of known races using an expanded set of differential cultivars. Plant Disease. DOI:10.1094/PDIS-04-11-0339.
Adhikari, T., Jackson, E.W., Gurung, S., Hansen, J., Bonman, J.M. 2011. Association mapping of quantitative resistance to phaeosphaeria nodorum in spring wheat landraces from the USDA National Small Grains Collection. Phytopathology. 101(11):1301-1310.